With the environmental reputation of 150 world leaders, including Prime Minister Justin Trudeau, riding on the outcome, the United Nations’ climate conference scheduled to wrap up Friday in Paris will be declared a historic success.

But it will be a failure because whatever agreement is reached at COP 21 (the 21st meeting of the Conference of the Parties), it will not include legally binding, enforceable greenhouse gas (GHG) emission reduction targets for the 190 participating nations.

That is what the UN has insisted for a quarter century is the only thing that can save the planet from runaway global warming caused by the emission of man-made GHGs when fossil fuels (coal, oil, natural gas) are burned for energy.

The failure to achieve it is why the UN’s Kyoto Protocol, approved in 1997 at Cop 3 in Kyoto, Japan failed.

It’s why the UN’s attempt to draft a successor agreement to Kyoto in 2009 at COP 15 in Copenhagen failed.

If past practice is any indication, the Paris conference will blow past its official Friday deadline amid breathless media reporting based on leaked information from the negotiators about how the negotiators are heroically working-round-the-clock on “humanity’s last chance” to “save the planet” from global warming, before a “miraculous” deal emerges on the weekend.

We’ve heard it all before -- including at COP 11 in 2005 held in Montreal during the dying gasps of the Jean Chretien-Paul Martin Liberal government, which ratified the Kyoto Protocol and then did nothing to implement it.

But Canada, responsible for 1.6% of global GHG emissions, is a bit player.

COP 21 will fail for the same reason COP 15 in Copenhagen failed, because neither China, the world’s largest GHG emitter, nor the U.S., the second-largest, will accept a binding treaty on reducing their emissions.

Indeed, the UN is twisting itself into a pretzel in Paris to avoid directly criticizing U.S. President Barack Obama, who at Copenhagen said a legally binding global treaty was ultimately needed to effectively combat climate change.

Now he doesn’t want one because he can’t get it through the Republican-controlled U.S. Congress, especially the Senate, which must ratify international treaties.

Because the UN knows no treaty has credibility unless the U.S., the de facto leader of the developed world, backs it, it has been tip-toeing around the fact Obama now opposes the very thing he said was needed at the start of his presidency to save the planet, when he foolishly boasted his election victory would mark, “the moment when the rise of the oceans began to slow and our planet began to heal.”

China, the leader of the developing world, has never budged from its position it will not accept binding targets to cut its emissions imposed by the UN, the U.S. or anyone else.

China argues the developed world owes financial reparations to the developing world for being the prime causer of global warming.

That’s why the UN wants Canada and other developed nations to contribute $100 billion annually to a so-called Green Climate Fund starting in 2020.

Indeed, that’s what the UN climate effort is really all about -- not reducing GHG emissions but global wealth redistribution.

As for emissions, the only time they’ve fallen is during recessions, when less fossil fuel is burned to produce energy, not because of anything the UN has done.